Heat exchanger



L. FRIEDMAN HEAT EXCHANGER June 20, 1950 Filed Jan. 13, 1948 PatentedJune 2Q, 1950 UNITED HEAT EXCHANGER Leopold Friedman, London, England,assignor to,

De la Rue Gas Development Limited, London, 7 England, a British companyApplication January 13, 1948, Serial No. 2,101

In Great Britain February 19, 1945 Y I Section 1, Public Law 690, August8, 1946" Patent expires February 19, 1965 This invention relates to heatexchanging devices employed with liquid heaters such devices comprisingone or more liquid fiow pipes fitted with metal fins, the hot gases fromthe combustion chamber passing over and between the fins to an outletflue.

The object of the invention is to provide an improved form of heatexchanger giving results similar to those obtained from the use of amultistage heat exchanger. A heat exchanger has been proposed comprisinga liquid fiow pipe bent to provide a series of parallel portions lyingin a common plane parallel to the direction of flow of the hot gases.The parallel portions of the flow pipe are each provided with metalfins, the superficial area of the fins increasing in the direction offiow of the hot gases. This increased area of the fins is obtained byincreasing the number of fins on the successive parallel portions of theflow pipe and at the same time decreasing their distance from oneanother.

According to the invention a heat exchanger comprises a straight flowpipe arranged horizontally, or a series of such pipes arranged in thesame horizontal plane which is transverse to the direction of flow ofthe hot gases, the pipe or the series of pipes having metal fins appliedthereto arranged in groups, the superficial area of the fins in thegroups increasing in the direction of flow of the hot gases, theincreased area of the fins being obtained by increasing the number offins in the successive groups and at the same time decreasing thedistance between them. The fiow pipe or pipes is or are arranged in asuitable casing through which the hot gases pass in any usual manner.The heating efiect obtained by the above arrangement is the equivalentof that obtained in a multistage heat exchanger.

The fins may be slotted and slipped over the pipes and secured theretoby brazing, soldering or in any usual manner.

To enable the invention to be fully understood it will now be describedby reference to the accompanying drawing, in which- Fig. 1 is a sideview of a single liquid fiow pipe arranged according to one form of theinvention, and

Fig. 2 is an end view thereof,

Fig. 3 is an end view showing an arrangement with three liquid flowpipes,

Fig. 4 is a side view and Fig. 5 is an end view of a further form of theinvention.

In the arrangement shown in Figs. 1 and 2, the underface of a straightflow pipe 6 is provided with spaced metal fins I and the upper 3 Claims.(Cl. 257-262.16)

. 2 surface of the pipe with an increased number of similar metal fins 8arranged at a decreased distance apart compared with the fins I.

Fig. 3 shows in end elevation an arrangement comprising three liquidflow pipes 9 arranged side by side in the same horizontal plane andfitted with top and bottom fins l0, ll corresponding to the fins 8, l ofFigs. 1 and 2. Any number of flow pipes may be so arranged in the samehorizontal plane.

Figs. 4 and 5 show a further arrangement. In this case a flow pipe l2 ofnon-circular crosssection is employed having fiat vertical sides l3.Four groups of fins are applied to the pipe. The fins It on theunderside are suitably spaced, a group I5 of increased number is appliedto each side l3 of the pipe above the fins l4 and spaced more closelytogether, the number of fins in each group I5 being equal and a group I6of a further increased number and still more closely spaced together isapplied to the top surface of the pipe.

The fins in this arrangement are shown as having tapered sides so thatthe cross-section of the device is trapezoidal, but they may be of anydesired shape and size.

A fiat-sided flow pipe is particularly well adapted for use according tothe invention as the flat sides provide suitable attaching surfaces forthe various groups of fins. As a flat pipe has two well-defined verticalsides arrangements are possible wherein each side of the pipe isprovided with fins arranged with different spacing to produce thedesired efiect.

It will be understood that the devices illustrated are arranged in asuitable casing through which the hot gases pass in any usual manner.

It will also be understood that the sizes or shapes and/or the thicknessof the fins in each group may be varied in any of the constructionscontemplated.

The fins may be slotted, as shown, to accommodate the pipes or attachedin any other convenient manner.

A heat exchanger for a liquid heater may comprise one section ofstraight horizontal flow pipes each arranged according to the inventionor a superposed series of such horizontal sections according torequirements, and the fin sizes and groupings on each section may besimilar or variations may be introduced as will be understood.

I claim:

1. In a heat exchanger of the kind referred to, a straight liquid flowpipe arranged in a horizontal plane transverse to the direction of flowof the hot gases, four groups of metal fins applied to the pipe, thoseon the underside being suitably spaced, a group of an increased numberbeing attached to each side of the pipe above those on the undersideandspaced more closely together, the nuinber of fins in each ofthesefside groups being equal, and a group of a further increased numberof fins on the top surface of the pipe the same horizontal plane whichis transverse to the direction of the flow of the-hot gases, each pipehaving four groups of metallfinsapplied thereto those on the undersidebeing. suitably spaced, a group of an increased number bein attached toeach side of the pipe above those on the underside 'and spaced more"closely together,

the number of fins in each or the side groups being equal, and a groupof a further increased number of fins on the top surface of the pipearranged still more closely together.

LEGPOLD REFERENCES CITED The fo1lowing references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 70,830 Thompson et a1. Oct. 4,1887 1524,1520 I'Junkers Jan. 27, 1925 1,911,522 McIntyre May 30, 19332,120,125 "Ca'ssidy et a1 June 7, 1938 FOREIGN PATENTS Number CountryDate Great'Britain Oct; 22; 51931

